The one-inch video broadcast machines presently in use in the television industry are designed to use metal reels for supplying and taking up magnetic tape for the machine. Light weight, usually smaller, and relatively inexpensive polymeric reels have recently come into use for storing and shipping one-inch videotape. While polymeric reels can be used on such video broadcast machines, they do not have the same moment of inertia as the metal reels for which the machine reel drives were designed, and thus can cause operational problems (particularly when such reels have little tape wound about them) such as instability of servo-systems in the reel drives when the reels are being slowed down, which causes improper movement of the tape across the tape head. Also, when such a polymeric reel is used as a takeup reel in combination with a metal tape supply reel and the machine is stopped, the plastic reel will stop more quickly than the supply reel, thereby causing a loop of tape to form between the reels that can damage the tape when the machine is re-started; and when such a polymeric reel is used as a supply reel in combination with a metal takeup reel, the plastic reel will again stop more quickly than the metal reel when the machine is stopped, causing the tape between the reels to be stretched and potentially damaged. Thus it has been found desirable to match the moment of inertia of polymeric reels with that of metal reels when polymeric reels are used on video broadcast machines.
One prior art method for providing a moment of inertia for a polymeric reel that approximates the moment of inertia for metal reels has been to insert weights into sockets formed around a hub portion of the polymeric reel and opening through a side surface of the reel. Known weights used for this purpose have comprised a heavy metal core encased in a resilient elastic material (e.g., rubber) and adapted to frictionally engage the walls defining the sockets in the reel. To use such weights, an operator presses each of three weights individually into one of three sockets around the hub portion of the reel, and after use must similarly pull each of the weights from within the sockets via a projecting handle portion on each weight.
While such weights can generally match the moment of inertia of the polymeric reel to that of the metal reels, their use is more inconvenient and time consuming than may be desired.
U.S. patent application Ser. No. 159,290, now U.S. Pat. No. 4,293,102, describes a weight assembly which is acknowledged as prior art to the weight assembly described in this application, which prior art weight assembly is adapted for use to generally match the moment of inertia of a polymeric reel with that of a metal reel, and is a one-piece unit that may be more quickly and conventionally inserted in and removed from the polymeric reel than the individual weights described above.
The weight assembly described in application Ser. No. 159,290 is for use on polymeric reels of the type comprising a hub portion having side surfaces, a through central opening, and a plurality of sockets opening through one side surface of the reel and spaced around the through opening. The weight assembly comprises a support plate in the form of an annular ring having a central opening larger than the through opening of the reel to afford engagement of the reel by the video broadcast machine, and a plurality of weights spaced around and projecting axially from the ring in the same direction, which weights were shaped and spaced along the ring so as to enter the sockets in the reel when the weight assembly is brought coaxially adjacent the side surface of the reel. Means are also provided for releasably attaching the weight assembly to the reel with the weights in the sockets and the ring portion coaxially adjacent the side surface of the reel to prevent the weight assembly from flying off the reel during operation of the video broadcast machine.
The means for attaching, however, comprises spring clips projecting axially of the ring from the same side of the ring from which the weights project, which spring clips were adapted to releasably engage walls defining orifices in the reel. With this arrangement, the weight assembly can be pressed into position with the weights in the sockets and the spring clips engaging the reel, and can then be easily released from the reel by impacting the side of the reel against an operator's hand with the ring portion adjacent his hand so that the spring clips release from the reel and the weight assembly can be separated therefrom. While such spring slips firmly engage the reel, however, they do not positively lock the weight assembly to the reel, and the specter remains that under some circumstances the weight assembly could separate from the reel during use of the reel on a video machine, which could cause damage to the machine or its operator.